Rail vehicle distance traveled measurements don't currently meet the precision requirement of 5ft./mile. An innovative microwave technique is proposed using two X band transceiver assemblies separated by a known distance. Reflected energy from metal objects such as tie-plates or dielectric contrast between ties and rail bed are used as replicate pairs to measure the time passage between transceivers using correlation techniques. Since the separation between transceivers in known a nearly instantaneous velocity can be computed at each tie. At 125mph this happens every 8636 microseconds. The velociy/time curve generated is integrated t get distance traveled. Time measurement precision is 5 to 10 microsecond-this ~1000:1 ratio provides the 1000:1 precision (5 feet/1 mile)required in distance traveled. Near field microwave devices are reliable in extreme weather conditions with a well designed hermetic housing and a microwave transparent window material. In Phase I a dual transceiver pre-prototype will be built. Testing includes gantry scanning, escalates to 125 mph in a laboratory test bed, and followed by rail cart tests on the experimental tracks at Texas A&M's TTI facility to measure dielectric contrast between ties and rail bed. Sensors are small (4"x4"x5"), lightweight, low cost, and battery operated.
